Eyeglasses not only serve to correct eyesight but are beneficial to protect eye cells from harmful light rays. Ultraviolet absorbing spectacle lenses containing ultraviolet absorbing agents that prevent transmission of ultraviolet rays are used for many eye protective gears, such as sunglasses and light-shielding eyeglasses.
Harmful light rays that should be blocked with such spectacle lenses include not only ultraviolet rays but infrared rays.
Of infrared rays, electromagnetic waves having a wavelength of 780 to 1300 nm, which are invisible, are called near-infrared rays, and electromagnetic waves having a wavelength of 1300 to 2000 nm, which are also invisible, are called middle-infrared rays. These infrared rays could penetrate the skin to the depth of as far as 30 mm. In particular, near-infrared rays could penetrate the cornea and almost reach the retina, thereby damaging the fundus oculi.
Eyes will suffer from thermal burns not only when momentarily exposed to intense infrared rays but also when infrared ray damage is accumulated over time, thus causing e.g. retinopathy and opaqueness of the crystalline lens (cataract).
Ordinary known infrared absorbing dyes that block transmission of infrared rays, i.e. dyes that can absorb infrared rays (which are also called infrared absorbing agents) include azo, aminium, anthraquinone, cyanine, polymethine, diphenylmethane, triphenylmethane, quinine, diimmonium, dithiol metal complex, squarylium, phthalocyanine and naphthalocyanine.
An infrared absorbing filter is known which includes an infrared absorbing layer formed by applying and drying a solvent-containing coating solution containing a resin composition comprising one or more of the above-mentioned infrared absorbing agents dispersed in a binder resin (Patent document 1).
A spectacle lens is also known which comprises a synthetic resin substrate having excellent optical properties as spectacle lenses, such as polycarbonate, diethylene glycol bis allyl carbonate (generally called “CR-39”), or polymethyl methacrylate (PMMA), and 0.001 to 0.05% by weight of some of the above-mentioned infrared absorbing agents (Patent document 2).
Patent document 1: JP Patent Publication 2005-43921A
Patent document 2: JP Patent Publication 2003-107412A (claims 2 to 4, paragraphs 0013, 0020, 0022 and 0023).